1. Field of the Invention
This invention relates to a coupling device of a charging connector assembly for an electric car and more particularly to a coupling device which can be operated under a relatively small force.
2. Statement of the Prior Art
Electric cars will find increasing use in the near further. As such, the problem of battery charging must be overcome. In particular, a charging connector assembly raises an important problem. The charging connector assembly comprises a car connector connected to a battery in an electric car and a charger connector connected to a charger through a cable.
A problem arises in that it is necessary to apply a large force to the charging connector in order to positively interconnect terminals in each connector. If a substantial load is caused due to friction resistance between the connectors during coupling, this may be mistaken for complete coupling. In the case of conducting a charging current through an assembly in an incomplete coupling state, the terminals generate heat or may spark when the connectors are displaced.
It is important to avoid a situation whereby a charging commences when a connector assembly is in an incomplete coupling state. Otherwise, abnormal heat may be generated in the assembly, oxidation due to sparks may be caused on the terminals in the assembly, or the assembly may impart an electrical shock to an operator.
There is a conventional charging connector in which one connector is provided on an outer periphery of an end with a male thread and the other connector is provided on an outer periphery with a rotatable ring which has a female thread adapted to be engaged with the male thread.
The connectors are electrically interconnected by being opposed with the rotatable ring being rotated so as to mate the male and female threads. The connectors are electrically disconnected from each other by turning the rotatable ring in a reverse direction.
In the conventional connector assembly mentioned above, the male and female threads are mated with each other by rotation of the rotatable ring to couple both connectors. However, coupling of thread engagement can be easily released.
In comparison with a car connector secured to the car, the charger connector is connected to the charger through the cable.
The charging connector assembly is of a relatively large size since a charging current is high and terminals are made large in size to accommodate a high current. Since the charger connector is connected to an end of the long cable, the total weight of the connector and cable is large. Accordingly, it is necessary to make handling of the charger connector easy before hand.
Both connectors must be locked to prevent the charger connector From falling off from the car connector after being coupled. However, an operator must continuously maintain a coupling force until a locking operation has been completed, which is tiring. If the operator releases his hold from the connector assembly when it is in an incomplete coupling state, the charger connector may be damaged.
A coupling device of a charging connector assembly for an electric car must maintain a car connector and a charger connector in a coupling state during charging and release the connectors from coupling after finishing charging. A coupling device having a lock piece is known which engages with, for example, the charger connector by rotation to maintain the coupling state of both connectors.
However, in the case of using such a coupling device, the operator must hold the charger connector by one hand and handle the lock piece by the other hand. Such handling will be troublesome for the operator. Further, the operator must handle the lock piece again to release the connectors after charging has finished.
In a real charging operation, the operator holds the charger connector and pushes it onto the car connector. If, in this case, insulation in the charger connector should deteriorate to leak out the charging current, a serious accident may occur.
As described above, it is necessary to take into consideration of coupling operation and safety of charging in designing of the charging connector assembly. For example, a mechanism for aiding a coupling force or a switch mechanism which permits conduction after confirming a safe condition is required. Particularly, it will be preferable to form the charger connector into a gun type shape in order to facilitate the coupling operation. In addition to the gun type shape, a lever may be provided to enhance handling of the coupling device.
However, even if the lever is provided on the device, it may be actuated before completing a condition of coupling aid and safety unless the lever is constrained from operating under an unsafe condition.